1. Process & Equipment – ECM’s

2. Common Energy Conservation Measures
ECM’s
Screening – very low energy use, look at control strategy
Influent pumping – maximize wet well level
Grit – Optimize blower use if aerated; change sheaves to reduce power use; pump only 15 minutes per hour
Primary – Remove as many solids as possible as it reduces load on aeration; sludge and scum pumping largest user in primary; optimize pumping
Secondary – blower use high – use inlet vanes, vari-speed blowers, fine bubble diffusers; DO control; optimize DO level; timers; speed control; control header pressure
Common Energy Conservation Measures (ECM’s)
Let us review of process options as they pertain to what we have discussed.
Screening. This is typically a low energy user because it usually uses small horse power motors.
But looking at the process side of the operation this is an option.
Look at the control strategy, the screen start and stop cycle, can it be adjusted to limit the run time? There are treatment plants that run the screens 24 hours a day. Maybe they should have time control or differential controls.
Influent pumping – Remember the impact of pressure on pumping cost. Can the wet well operating level be adjusted to reduce the pumping head? Just a small decrease in pressure or head can save 2 to 4 percent or more in energy.
Grit- If we have an aerated grit chamber, change the blower sheaves to reduce the air volume and power use, or consider short run time cycles. Remember we are trying to create a rolling action, not aerate the contents to get a dissolved oxygen. We do not want to be blasting a lot of air that really is not necessary. If there is a pump system for removing the grit, can the run time cycle for removal be adjusted?   
With primary sedimentation the goal is to remove as many solids as possible, as this will reduce the load on the aeration tank and associated running of the process blower. Sludge and scum pumping are the largest users of power in primary, so look for opportunities to optimize the pump cycles.
As far as secondary treatment is concerned aerated tanks are a must, therefore blower use is high energy. Inlet vanes or valves are typically used to control air flow rates. Options to consider include dissolved oxygen probes and D.O. control. Consider the use of fine bubble diffusers to get better oxygen transfer.
Another parameter to consider is pressure control on the air header, since we now know higher pressure costs energy. A new turbine type of blower is now being used that is more efficient than your standard centrifugal blower, plus it is more suitable to using a VFD. This will improve our ability to deliver the right amount of air.

3. Common ECM’s
RAS pumping can be significant since it is 40 to 100% of total forward flow. Time cycles
WAS pumping only 1 to 3% of influent flow, but may have a high head
Disinfection – low use, but high use of energy to produce hypochlorite or UV
Filtration – most energy use in backwashing, esp if air scour; if demand billing, may be able to backwash at off-peak power rates
Common ECM’s
Another process related energy conservations measure includes the return activated sludge pumping. This process involves being able to pump a volume equal to 40% to 100% of total forward flow. We may want to consider time cycles. Most of the time many systems already have VFD control, so it may be a matter of maintaining a certain blanket depth. Consider time cycles, but cautiously so we do not impact the process itself. Time cycles are not appropriate with a single pump and clarifier, but are an option with multiple system. This way sludge can be continuously returned to the process.
Waste activated sludge (WAS) pumping is usually a small percentage of the flow. Normally WAS is approximately 1% to 3% of treatment plant influent flow. Generally speaking with WAS we want it to be as thick as possible to avoid sending to much liquid volume to the sludge handling system.
Disinfection is a low use, but high energy to produce hypochlorite or if you are using Ultraviolet (UV) light you may have high energy use. With UV it is about process efficiency, so maintenance of the bulbs and tubes are critical.
As far as filtration, most energy use is in the backwashing, especially if it also uses an air scour. The backwash process is the perfect opportunity to do off peak operation if that is part of the tariff.

4. Common ECM’s
Sludge Thickening – Gravity thickening, rotary drums, and belt thickeners are low energy consumers
Sludge stabilization – aerobic digestion is a high energy user, using a blower to introduce air. Anaerobic digestion is a producer of energy. It only requires mixing. Mix intermittently; interim operation of heater recirculation pumps; mix/recirculate off-peak hours
Sludge dewatering – belt presses use low energy; centrifuges are high energy consumers, however produce a drier cake; filter presses use moderate energy and produce a drier cake
As far as process options for sludge thickening, gravity thickening, rotary drums, and belt thickeners; these processes are usually low energy consumers. There is not a lot to find in savings here.
Sludge stabilization – if using aerobic digestion it is usually a high energy user. As mentioned earlier an option is to consider ON and OFF cycles for the air system. This option will also improve the process by reducing the nitrate concentration in the decant liquid.
Anaerobic digestion is typically a producer of energy. It only uses energy when mixing which the process requires. Consider mixing intermittently or interim operation of heater recirculation pumps. Mix and recirculate during off-peak hours.
When sludge dewatering using belt presses is preferred as they are low energy users. Centrifuges are high energy users, but they can produce a drier cake; filter presses use moderate amounts of energy and produce a drier cake as well. Drier cake is the goal here, because we do not want to pay for the disposal of liquid.

5. Common ECM’s Pumps Vary RAS pumping with sludge blanket levels
Run RAS in on/off mode, esp. with nightly low flows(CAUTION)
If have multiple pumps give more run time to most efficient pumps
If several large pumps consider having a smaller pump to handle lower flow periods
Increase wet well level or reduce pumping head
Add VFDs
Timers for on/off operation
Reduce recycle flows (filter wash, foam sprays etc.)
Flush lines periodically
Trim impellers
Some additional process ECM options for pumping includes varying the return sludge pump speed to correspond with rising or falling sludge blanket levels. Blanket detectors have become more reliable and this is a good control strategy for RAS control.
Another option is to operate the Return Sludge pump in on and off cycles. We want to be careful with this option as it can create problems in the sludge quality. We can especially do this at night time when flows are low to start with and we are typically slowing down the pump considerably.
If we have multiple pumps, give more run time to most efficient pump, or if there are large pumps consider having a smaller pump to handle the lower flow periods.
Increase the wet well level or reduce pumping head and if you can add VFDs, again not as something that is going to necessarily have to pay for itself, but we can do it as an upgrade.
Use timers for on and off operations, reduce recycle flows such as filter backwash, foam sprays etc.
Flush the lines periodically to remove any accumulations that could be creating head in the lines and trim the impellers.

6. Common ECM’s Activated Sludge Systems D.O. Control ON/OFF Timer
Diffuser Cleaning & “Bumping the Diffusers
Convert from Course Bubble to Fine Bubble
Lower D.O. setpoint
Adjust air drop valves
D.O. sensor location
Reduce number of aeration basins
Reduce pounds of solids
Look for boils or unusual bubble pattern
Replace or clean fine bubble diffusers
Common ECM’s
When it comes to activated sludge systems, ECM options for DO control includes:
On and off timer control for blowers or air drops valves,
Diffuser cleaning and bumping the diffusers,
Converting from course bubble to fine bubble diffusers,
Lowering the D.O. set point,
Adjusting the air drop valves – maybe we do not have a way of controlling each air drop, but we can adjust the air valves going to the air drop.
Putting D.O. sensors in the correct locations,
Reducing the number of aeration basins in service especially if we have multiple trains available maybe we do not need to have air going to all of them,
Reducing the pounds of solids under aeration, but do not reduce the pounds of solids to the point where it impacts BOD, ammonia and nitrate removal,
Looking for boils or unusual bubble patterns in your reactors or aerated zones, and
Replacing or clean fine bubble diffusers. A membrane type of diffuser is typically replaced every 5 to 7 years.

7. Common ECM’s Blower Systems Repair leaks
Perform O & M – Clean Filters, bearing lubrication
Blower intake use outside air vs room air
Clean and check D.O. sensors periodically
Reduce air header pressure if possible
Adjustable speed blowers
New Blower technology – Turbo Blowers
Reduce air flow where possible
Two blowers ON can one handle demand
Common ECM’s
For blower systems make sure leaks are repaired, and typical O and M tasks such as cleaning the filters, and bearing lubrication are performed.
The blower intake uses outside air vs room air. Is it possible to use inside air since it should be a clean source?
Clean and check the D.O. sensor periodically, a lot of places have a laboratory instrument that they use for calibration checks of their field instruments periodically.
Reduce the air header pressure by better control of the air flow rates and balance air flow rates to meet the need of a specific zone. Use adjustable speed blowers.
Consider a new technology that uses turbo blowers which are more suitable for VFD control. Reduce air flow where possible and only use one blower if it can handle the demand.

8. Benefits of High Efficiency blowers
Remember that aeration is the biggest part of the energy cost at our plants. This slide reinforces the fact that energy consumption account for 75% of the cost associated with the blowers.
That is a great opportunity to reduce energy costs. The turbine style blowers offer greater efficiency and the ability to turn down air flow rates over a larger range without the worry of blower surge.

9. Common ECM’s Mechanical Mixing Systems Confirm Submergence depth
Perform O & M – Check for accumulations
Reduce the number of mixers if possible
Consider not mixing pumped recycle zone
Looking at the mechanical mixers, we want to make sure that the submergence depth is what is recommended.
Perform the operation and maintenance checks and include checking for accumulations on the mixer. Anything running around in circles with that mixer is probably causing extra energy consumption by creating drag.
Reduce the number of mixers if possible.
Consider not mixing in the pumped recycle zone. Again, that is another case where we look at the nitrate recycle zone and since we have pumped recycle going to this zone, maybe it is not necessary to also run a mixer in this zone.

10. Other Systems
Ventilation & Odor Control - Reduce air flow to minimum needed to control odor and ensure required air changes per hour
Can the system only be run seasonal when odors are the worst
Can ventilation be run on/off cycles
Ultraviolet System – keep lamps clean and remove scaling
Replace lamps with high output lamps
Lighting – Turn off unneeded lights
Use occupancy sensors
Switch bulbs (T5,LED)
Laboratory- Turn off muffle furnace and unused equipment
Other Systems
Discussing other systems, for ventilation and odor control we should ask,
Can air flow be reduced and still scrub the air, or can the system only be run seasonally when odors are worst?
Run certain ventilation equipment in on and off time cycles. With Ultraviolet disinfection systems keep the lamps clean, remove scaling buildup from the tubes, and replace lamps with high output lamps.
For lighting systems remember to turn off unneeded lights, use occupancy sensors, and switch bulbs to the T5 or LED type.
For the laboratory equipment, do we have a muffle furnace we are leaving it on all day long when we may only be using it for a test once or twice a week, and are just leaving it on all the time?

11. Building HVAC Systems
Can area heater /air conditioning only be used only when people are working the area
Clean air filters
Have units tuned for maximum efficiency
Use automatic thermostats
Use timers or occupancy sensors
Can heat from blower room be directed to other area
Can boiler heat be directed elsewhere
Building HVAC Systems
In building HVAC systems, ECMs to consider include questioning if area heat or air conditioning systems can be used only when people are working in the area?
Look for the low hanging fruit with HVAC system, we are all guilty of running HVAC equipment because it is there, not necessarily because we need it. Thinking about energy, if a 5 kilowatt unit is running constantly, it is costing a 5 kilowatt demand plus energy consumption at that rate for every hour it is running.
Other options typically used, includes cleaning or replacing air filters, tuning units for maximum efficiency, using automatic thermostats, using timers or occupancy sensors, etc.,
Another new concept may be, can we take heat from the blower room so it can be directed to other areas? You know the blower room is probably the hottest place in the plant, can we use that heat somewhere else?

12. Plant Process Control Systems
Many of the newer systems use graphic screens similar to this to show Power Data on a continuous basis. With this graphic page we see the total plant power data including amps and volts.

13. Plant Process Control Systems
This is another screen of a control system. It provides kilowatt demand data and power. So again, screens like this may help us visually see what our system or a piece of equipment is doing.
Monitor a screen like this to see changes in KW when equipment is either started or stopped.

14. Last but not least, this booklet is an EPA document that is available for your use. It provides you guidance to help set up an energy conservation program and is included in your course materials.